This invention relates generally to apparatuses for detecting and locating the area of apparent concentration of unbalanced weight or mass in unbalanced rotating bodies and more particularly, it relates to an improved pick-up unit which finds application in balancing rotating bodies such as vehicle wheels by utilization of a stroboscopic light type to detect and locate the area of apparent unbalance.
The apparent area of unbalance in rotating bodies heretofore has been detected and located by various ways. Conventional stroboscopic type unbalance detection apparatus utilizes either a velocity pick-up or an acceleration pickup which follows the vibrations of the rotating body and generates a corresponding signal. Such pick-ups usually comprise a permanent magnetic core and a multi-turn coil, the core and the coil being movable relative to each other to generate the corresponding signal. It is known for a fact that the displacement of the unbalanced rotating body will lag the locus of the unbalanced mass by 90.degree. when the rotational speed coincides with the critical or resonant speed of the rotating body. Thus, compensator circuitry such as 90.degree. phase shifter networks were required in such prior art pick-ups to properly synchronize the stroboscopic illumination with the rotating bodies so as to detect and locate the apparent area of unbalance.
It has been discovered by the use of a new and novel pick-up unit of the displacement type simpler and less expensive electronic circuitry may be utilized to trigger the stroboscopic light in synchronization with the unbalanced rotating body so as to detect and locate the apparent area of unbalance.